Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $195.50   4.380%   $204.0629   $204.06   $204.05   $204.10  
  Purchase #2 $188.86   6.690%   $201.4947   $201.49   $201.50   $201.50  
  Purchase #3 $33.85   7.106%   $36.2554   $36.26   $36.25   $36.30  
  Purchase #4 $219.31   3.426%   $226.8236   $226.82   $226.80   $226.80  
  Purchase #5 $98.74   4.705%   $103.3857   $103.39   $103.40   $103.40  
  Purchase #6 $62.47   7.518%   $67.1665   $67.17   $67.15   $67.20  
  Purchase #7 $153.63   10.414%   $169.629   $169.63   $169.65   $169.60  
  7 purchase totals = $952.36       $1,008.8178   $1,008.82   $1,008.80   $1,008.90